RU2763277C1 - Cutting assembly - Google Patents

Abstract

FIELD: cutting.

SUBSTANCE: invention relates to the cutting assembly for mining or earthmoving works. The cutting assembly of the rock cutting machine comprises: the main unit, one or more mobile support arms extending from the main unit, a spindle attached rotatably to said or each mobile support arm, a disk cutter secured relative to the spindle so that rotation of the spindle causes the corresponding rotation of the disk cutter. The disk cutter therein comprises a cutter body, a set of cutting elements, and a corresponding amount of tool holders, namely, one for each cutting element, wherein the cutting elements and tool holders are arranged around the circumferential surface of the cutter body. Each cutting element is placed in the socket of the tool holder, wherein the socket is oriented so that the cutting element is directed in a predetermined direction of rotation or thereto. The cutting element is therein cylindrical and has a flat cutting surface, said or each cutting element is a polycrystalline diamond compact (PDC), the size in the lateral direction of each cutting element is greater than the size in the lateral direction of the tool holder.

EFFECT: protection of the tool holder by the cutting element from significant wear during operation, increasing the operating life of the cutting element.

11 cl, 11 dwg

Description

Technical field

The invention relates to mining and earth-moving machines. In particular, it relates to the cutting unit of a rock excavation machine.

Prior Art

Numerous types of rocks found throughout the world in the form of large deposits are commonly known as strata. Various types of mining equipment are used to excavate seams from the ground in surface quarries. These formations are mined using special equipment, usually hauled from their location by large and very powerful vehicles. Rock layers can weigh up to 40 tons (40,000 kg). Processing, such as polishing, may be performed on site, or alternatively, the sheets may be transported from the excavation site to be cut into pieces of appropriate sizes for domestic and industrial use.

The same equipment used on land may not always be used directly in the confined space of an underground mine.

The objective of the invention is to provide a compact universal cutting unit for facilitating the development and excavation of geometric and non-geometric blocks of specific rocks and a unit that can be used for ground or underground work.

Disclosure of invention

According to the invention, the cutting assembly of a rock excavation machine comprises: a main block, one or more movable support arms extending from the main block, a spindle rotatably attached to said or each movable support arm, a disk cutter fixed relative to the spindle so that rotation of the spindle causes the corresponding rotation of the disk cutter, and the disk cutter contains a cutter body, a plurality of cutting elements and a corresponding number of tool holders, namely, one for each cutting element, while the cutting elements and tool holders are located around the circumferential surface of the cutter body, each cutting element is placed in the seat of the tool holder, the seat is oriented so that the cutting element is directed in the specified direction of rotation or towards the specified direction of rotation.

In some embodiments, the tool holders extend radially outward from the cutter body.

Preferably, the rake angle of the cutting element relative to the tool holder is 10 to 30 degrees. Optionally, the rake angle is approximately 25 degrees.

The tool holder can be permanently connected to the cutter body, for example by brazing. Alternatively, the tool holder may be releasably connected to the cutter body. According to an embodiment, the tool holder is releasably connected to the cutter body by means of a locating pin.

Each cutting element can be permanently fixed in the socket by brazing. According to an embodiment, the cutting element may be rotatably mounted in the socket.

Optionally, the tool holder is generally frustoconical when viewed in the axial direction and has a shorter front side than the back side, with the seat located on the front side.

Optionally, the cutting element is cylindrical and has a flat cutting surface. Said or each cutting element may be a polycrystalline diamond insert (PDC).

In some embodiments, the side dimension of each cutting element is larger than the side dimension of the tool holder. According to such embodiments, the cutting element optionally protrudes laterally beyond the tool holder by at least 1 mm on each side.

Each tool holder may taper laterally inwards from the cutting element towards the cutter body.

Brief description of the drawings

The following is a detailed description of the invention by way of example only, with reference to the drawings.

In FIG. 1 schematically shows an underground working comprising a cutting assembly according to the first embodiment, which is part of a longwall mining system, the cutting assembly being shown in a horizontal orientation, top view;

in fig. 2 is the longwall mining system of FIG. 1, side view;

in fig. 3 is an underground working containing a cutting assembly according to the second embodiment, which is part of a longwall mining system, with the cutting assembly shown in a vertical orientation, top view;

in fig. 4 is the longwall mining system of FIG. 3, side view;

in fig. 5 is a disk cutter according to the first embodiment, front view;

in fig. 6 is a cutting element for use with the disc cutter of FIG. 5, front view;

in fig. 7 - cutting element in Fig. 6, side view;

in fig. 8 is a disk cutter according to the second embodiment, a front perspective view;

in fig. 9 is a plurality of cutting elements for use with the disc cutter of FIG. 8, side view;

in fig. 10a is the first single cutting element in FIG. 9, side view;

in fig. 10b is the second separate cutting element in FIG. 9, side view.

In the drawings, like parts are indicated by like reference numerals.

Embodiments of the invention

In FIG. 1 and 2 show, generally referred to as "10", a cutting assembly for mining layers of natural subterranean rocks 2.

The cutting assembly forms part of a longwall mining system 1 commonly used in underground workings. The cutting unit is a substitute for the well-known cutter, which operates on the working horizon 4 of the mine between the group of adjustable sections 6 of the support. As the cutter advances towards the mine, the lining sections 6 are positioned so as to support the roof 8 of the run directly behind the cutter. Behind the sections 6 of the support, the roof 8 of the excavation collapses in a relatively controlled manner. The raking paw collects the rock mass on the cutting side and transfers it to the transport system for subsequent removal from the mine.

In the first embodiment shown in FIG. 1 and 2, the cutting assembly 10 comprises a main block 12, a pair of spaced support arms 14 extending from the main block 12, a spindle 16 extending and rotatably mounted between the pair of movable support arms 14, and a plurality of disc cutters 18 fixed relative to the spindle 16.

In the second embodiment shown in FIG. 3 and 4, a single support arm 14 extends from the main assembly 12. The spindle 16 is supported centrally by the single support arm 14, and a plurality of disc cutters 18 distributed on each side of the single support arm 14 are mounted on the spindle 16.

In another embodiment, which is not shown, only one disc cutter 18 is used.

Preferably, said or each disk cutter 18 is mounted centrally (i.e., centrally located) relative to the spindle 16. However, this is not essential, and the specified or each disk cutter 18, as an option, can be installed off-center relative to the spindle 16. A combination of these two locations may be used at your discretion. For example, when a plurality of disc cutters 18 are arranged in series, i. e. parallel to each other along spindle 16, alternating disc cutters 18 may be centered relative to spindle 16. The center of each of the remaining disc cutters 18 may be radially offset from the point at which disc cutter 18 is mounted relative to spindle 16. Other combinations may be used.

The main block 12 acts as a conveyance system for the cutter 18. The main block 12 is movable and advances or retracts the cutter 18 in the vicinity of the rock 2 to be cut. The speed at which the main block 12 moves next to the rock 2 is one of several variables that determine the feed rate of the cutting assembly 10 in the rock 2. The main block 12 (in cooperation with the lining sections 6) can also move laterally from left to right. and vice versa along the longwall of rock 2 to be mined.

Each support arm 14 is movable in first and second cutting orientations. In the first cutting orientation, most clearly shown in FIG. 1 and 2, the spindle 16 is horizontal. As a result, the cuts in the rock 2 made by the disc cutter 18 are respectively vertical. In the second cutting orientation, most clearly shown in FIG. 3 and 4, the spindle 16 is vertical. As a result, the cuts in the rock 2 made by the disc cutter 18 are respectively horizontal. First and second cutting orientations may be possible with any of the above embodiments, first or second.

Optionally, the support arm(s) 14 can also be movable so that the spindle 16 can be operated in any cutting orientation between the above vertical and horizontal, although this is not essential. Alternatively, the support arm(s) 14 may be configured to move between the first and second cutting orientations only when fully operational (i.e., the disc cutter(s) must be rotated to facilitate cutting or comminution of the rock. ) in the first and second cutting orientations.

Each support arm 14 is movable between a first operating position and a second operating position, with each of the first and second cutting orientations optionally required depending on the depth of cut. This is shown by the double arrow A in FIG. 2. For example, in the first working position, the spindle 16 is lowered so that it is near the working horizon 4, and in the second working position, the spindle A is raised so that it is near the roof 8 of the working.

Optionally, each support arm 14 may have a first arm portion connected to a second arm portion by an articulated joint (or, alternatively, by a universal joint), each first and second arm portions being movable independently relative to one another. This design increases the number of degrees of freedom with which the cutting assembly 10 can operate and advantageously improves its maneuverability.

The spindle 16 is driven by a motor to rotate at a particular speed. The motor power is 20 - 50 kW per cutter 18, depending on the type of cutter 18 selected and the required cutting force.

As most clearly shown in FIG. 5, according to one embodiment, the disk cutter 18 has a round body 20 and a plurality of cutting elements 22 located peripherally around the round body 20. The rotation of the spindle 16 causes the disk cutter 18 to rotate accordingly. However, the disk cutter 18 does not have to be round and can only be generally round, for example, depending on the size, an octagonal cutter could approximately correspond to a generally round disc cutter. Accordingly, the disc cutter 18 may be hexagonal, octagonal, decagonal, and so on. or, in fact, may have any number of sides extending in the circumferential direction.

The specified or each disk cutter 18 may also contain one or more sensors. These sensors may be embedded or embedded in the body 20 of the cutter. The sensor may be any of the following sensors: a temperature sensor, a pressure sensor, an x-ray sensor, a gamma ray sensor, an acceleration sensor, a sensor capable of monitoring the chemistry of cutting conditions, or a sensor for identifying rocks or materials to cut. According to such an embodiment, the sensors may be connected to the data acquisition system and potentially also be connected to the data analysis package online or remotely from the site of the mining/excavation operation.

According to a preferred embodiment, a plurality of disc cutters 18 are located on spindle 16. Six or more disc cutters 18 may be provided. shoulder 14 depending on the embodiment.

The distance between the disc cutters 18 is selected depending on the desired depth of cut and the mechanical properties, such as the tensile strength (UTS) of the rocks 2 to be cut, to optimize the specific cutting energy that determines the required power consumption. The task is to provide conditions under which the cut material will collapse under the action of its own weight. For example, for a depth of cut of 0.4 m in kimberlite, the ideal distance between adjacent disc cutters is approximately 0.3 m. However, this can be increased or decreased depending on the force required for caving. Preferably, the distance can be adjusted in situ by an automatic process or a manual process. The distance can be adjusted remotely, for example, from a ground control station. A wedge-shaped tool can be used to apply such a collapse force that promotes collapse of the rock.

The disc cutters 18 are spaced at a spacing of preferably 0.01-2 m, more preferably 0.01-0.5 m. Even more preferably, the disc cutters 18 are spaced 10-40 cm apart.

The round body 20 of the disk cutter 20 is made of steel and has a diameter of approximately 1000 mm and a thickness (measured in the axial direction and in the following description also referred to as a dimension in the lateral direction) of approximately 11 mm. In fact, this diameter provides a cutting depth of up to 400 mm. The round body 20 has a diameter 23 of the hole for the spindle, which is 60–100 mm, and the dimensions and shape of this hole make it possible to place the spindle 16 in it.

The diameter (or effective diameter in the case of non-circular disc cutters) and thickness of the disc cutter 18 are selected appropriately depending on the purpose of the cutting assembly. For example, in the case of cabling, a disc cutter 18 with a smaller diameter is required. Angle grinders with a robotic arm would require an even smaller cutter diameter. Tunneling would require a disc milling cutter 18 with a considerably larger diameter and appropriate adaptation.

According to this embodiment, the disk cutter 18 also includes a plurality of tool holders 24 to accommodate a corresponding number of cutting elements 22. According to another embodiment, the disk cutter includes one or more tool holders.

Preferably, although it is essential, each tool holder 24 has a socket for receiving one cutting element 22. Preferably, each tool holder 24 is made of steel, but may alternatively contain any metal(s) or carbides or ceramic based materials. with a hardness above 70 HV (Vickers hardness). Each tool holder 24 may be permanently connected to the cutter body 20 (eg, by brazing or welding) as in the embodiment shown in FIG. 5, 6, and 7, or it may be releasably connected to the cutter body 20 by means of a locking mechanism, as in the embodiment shown in FIG. 8, 9 and 10a and 10b. A combination of brazing, welding and/or mechanical connections may be used. Alternatively, the tool holder(s) 24 may be integrally formed with the body 20 of the cutter 18, such as by forging, powder metallurgy, and the like.

The locking mechanism may include a locating pin that is used to attach the tool holder 24 to the cutter body 20. Alternatively, clamping, hot pressing, etc. can be used.

According to an embodiment, each cutting element 22 is rigidly or fixedly supported by one of the tool holders 24. Each tool holder 24 is preferably positioned at an equal angular distance around the circumferential surface of the cutter body 20. Each cutting element 22 may be secured in place in or on the tool holder 24 by brazing. Alternatively, either or each tool holder 24 may be configured to rotate the cutting element 22. In such an embodiment, the cutting element 22 and the tool holder 24 may be configured such that the cutting element 22 is free to rotate in the tool holder 24, for example , with a loose fit, or alternatively could rotate in the tool holder 24 only when the cutting element 22 comes into contact with the rock to be excavated/excavated, for example, using a transition fit.

Each of the cutting elements 22 contains a hard wear-resistant material with a hardness of 130 HV and above. The cutting element 22 preferably contains an ultra-hard material selected from the group consisting of cubic boron nitride, diamond, diamond-like material, or combinations thereof, but may instead contain a hard material, such as tungsten carbide. The cutting element 22 may comprise a cemented carbide backing to which a superhard material is bonded.

In an embodiment, the cutting elements 22 are polycrystalline diamond (PDC) inserts commonly used in the field of oil and gas drilling. Such PDCs are often cylindrical and typically contain a diamond layer sintered to a steel or carbide substrate.

The PDC has a diameter of 6-30 mm, preferably 8-25 mm. For example, the PDC may have a diameter of 13 mm, or 16 mm, or 19 mm. Preferably, the PDC has a diameter of 16 mm. In a disc cutter, a combination of diameters can be used.

Each PDC may have bevels, double bevels, or multiple bevels.

Each PDC may comprise a polished cutting surface or may be at least partially polished.

Alternatively, the cutting element 22 may be a 3-D cutter, in contrast to a conventional PDC. The impact end of the cutting element 22 may be conical, pyramidal, ballistic, chisel-shaped or hemispherical. The impact end may be truncated with a flat top or non-truncated. The impact end may be axisymmetric or asymmetric. Any form of cutter 22 may be used in conjunction with an aspect of this invention. Examples of such cutters are given in WO2014/049162 and WO2013/092346.

In the first embodiment of the tool holder 24, as shown in FIG. 5, 6 and 7, each tool holder 24 is generally frustoconical in shape when viewed in the axial direction (see FIG. 6). Each tool holder 24 has a front side 26 and a back side 28, with each cutting element 22 located in a socket 30 on the front side 26 of the tool holder 24. Each seat 30 is angled so that the cutting element 22 faces tangentially (or more generally towards) in a predetermined direction of rotation. This is particularly suitable for PDCs that have a flat main cutting surface 32. Due to the socket, the cutting edge 33 of the cutting element 22 can be oriented in a range of angles relative to the cutter body 20, which is different from the traditional approach where the existing cutting elements 22 are directed exclusively outward. in a radial or axial direction towards the rock surface. This provides greater flexibility to obtain the desired cutting angle without the need to modify the design of the impact end of the cutting element.

In addition, the provision of a pocket to accommodate a separate cutting element 22 means that, as an advantage, excess PDC stock can be used and useful in a new application, thereby reducing the company's working capital.

Optionally, the main rake angle of the cutting element is 25 to 30 degrees. Optionally, the main rake angle is 25 degrees. The leading rake angle can be positive or negative as desired.

The front side 26 of the tool holder 24 is generally shorter than the rear side 28, which provides significant rear structural support for the cutting element 22 during use. The tool holder 24, in particular the rear side of the tool holder 24 in the direction of rotation absorbs a significant amount of shock during operation and reduces the risk of the cutting element 22 "jumping" out of the cutter body 20 and being lost.

Preferably, the socket fully supports the back surface (i.e., the surface that is generally opposite to the cutting surface 32) of the cutting element 22.

In the side view (see FIG. 7), each tool holder 24 has a variable side section. Each tool holder 24 tapers laterally inward from the head 34 of the tool holder 24 adjacent to the cutting element 22 to a base 36 adjacent to the round body 20.

The lateral dimension (most clearly shown in FIG. 7) of each cutting tool 22 is larger than the lateral dimension of the tool holder 24. This protruding part protects the tool holder 24 from significant wear during operation. Preferably. the thickness (i.e., dimension in the lateral direction) of the tool holder 24 is approximately 14 mm. According to this embodiment, the cutting element 22 protrudes from the tool holder 24 by approximately 1 mm on each side. This ensures that it is the cutting element 22 and not the tool holder 24 or the cutter body 20 that is subjected to most of the wear during use. The protrusion prevents the tool holder 24 from rubbing against the rocks 2. In case of friction, a hard coating or multi-layer coating can be used.

In the second embodiment of the tool holder 24, as shown in FIG. 8 and 9, successive tool holders 24 are laterally displaced relative to the cutter body 20. As shown in FIG. 10a and 10b, each tool holder 24 has a slight kink to one side. In other words, the distal portion 24a of the tool holder 24 is laterally offset from the cutter body 20 and the proximal portion 24b of the tool holder 24. The distal and proximal parts 24a, 24b are oblong in the lateral direction. The distal and proximal portions 24a, 24b of the tool holder 24 converge at an intersection indicated generally as reference "38". The lateral displacement direction is either a first direction extending axially from one side of the cutter body 20 or a second opposite direction extending from the other side of the cutter body 20. In FIG. 10a, the tool holder 24 is kinked to the right, and in FIG. 10b, the tool holder 24 has a kink to the left. Intersection 38 may be an abrupt change in direction, such as a sharp bend, or a prolonged change in direction, such as an arc. Intersection 38 may include a middle portion connecting the distal portion 24a to the proximal portion 24b.

Alternatively, the proximal portion 24b may be laterally offset from the cutter body 20 while the distal portion 24a may be aligned with the cutter body 20. However, since the cutting member 22 is disposed on the distal portion 24a of the tool holder 24, the first mentioned structure is preferable.

The direction of lateral displacement of successive tool holders 24 alternates along the circumferential surface 40 of the cutter body 20 . This design has the advantage that it increases the effective cutting area of the cutting elements 22 during rotation of the round body 20, regardless of the size of the cutting element 22. It also facilitates quick and easy replacement of the individual tool holder 24 during maintenance and repair without the need to remove the entire body. 20 cutters. In addition, this design helps to reduce the erosion of the cutter body 20 (sometimes referred to as "body washout") caused by the flow of cut rock behind the cutting assembly 10.

The cutting assembly 10 may further comprise a surface hardening material (not shown). The surface hardening material may contain a low melting point carbide (LMC) having an iron base. Examples of materials are described in US8968834, US8846207 and US8753755, although other wear resistant materials may be used instead. The purpose of the material to increase the surface hardness is to limit the "washout" of the body 20 of the cutter. The surface hardening material may be rotated behind the tool holder 24 near the rear side 28. If the tool holders 24 are spaced apart, the surface hardening material may be located in or on the cutter body 20 between successive holders of 24 tools. Additionally or alternatively, the surface hardening material may be present on the rear side 28. Additionally or alternatively, the surface hardening material may be present on the front side 26. The surface hardening material may be present on the front side 26, the back side 28 and circumferential surface 40. The location of the surface hardening material on the cutter body 20 and/or tool holder 24 depends on the specific conditions and is selected depending on the nature of the rocks being mined at that location.

During operation, the disc cutter 18 comes into contact with the rocks 2 and the rotation of the spindle 16 and hence its disc cutter(s) causes the rock to be cut in 2 layers. The cutter assembly 10 cuts the rock in 2 layers, for example, producing clean perpendicular cuts of approximately 16 mm, depending on the size of the cutters 22 selected.

Although several applications of the cutting assembly have been described above, tunneling is a particularly effective application. A tunnel boring machine (TBM) is usually used to create a new underground tunnel. The TBM forms a cylindrical tunnel in a well-known manner. If the tunnel is intended for vehicular or pedestrian traffic and it is possible to obtain a circular tunnel, the lower part of the tunnel should contain a new horizontal canvas. In fact, the diameter of the tunnel is very large. Excess rock material must be excavated to create the actual usable space within the top of the tunnel, which increases the cost of tunneling not only because a larger TBM requires more cutter ends than a smaller TBM, but also because the operation of tunneling requires much more time. In addition, additional material is required to build a new canvas. Thanks to the described cutting unit, a tunnel of smaller cross section can be built to obtain the desired shape of the upper tunnel. The cutting assembly follows the smaller TBMs to form the bottom half of the tunnel and produce a blade perpendicular to the walls, removing significantly less material than the larger TBMs.

While the invention has been explained and described in detail with reference to embodiments, those skilled in the art should appreciate that a number of changes in form and construction may be made without departing from the scope of the invention as defined in the claims.

For example, in the second embodiment of the cutting assembly, although only one support arm 14 has been described, there may be two or more spaced support arms 14.

For example, the two embodiments described herein include a plurality of disc cutters 18 mounted on a spindle 16. This is optional and a single disc cutter 18 may be used.

For example, instead of using a combination of paired cutting elements 22 and tool holders 24, the cutting elements can be built directly into the body of the disk cutter 18 at its peripheral edge, thereby eliminating the need for an intermediate tool holder 24.

For example, said or each cutting element may contain crystalline diamond instead of polycrystalline diamond material.

For example, the cutting element 22 may comprise a diamond or a metal coated with abrasive grit, or may be ceramic-based.

While the cutting assembly 10 has been described as being useful for underground work, it can equally well be used in surface operations, such as in an open pit.

In addition, this small-sized assembly can be used for digging micro-trenches in the roadway and bridges, for example, for laying small-diameter fiber optic cables. In this case, the cutting unit 10 cuts into asphalt and concrete, and not into rock. According to such an embodiment, the diameter of the cutter body 20 is in the order of 300 mm, the thickness of the cutter body in the lateral direction is up to 20 mm, and the cutting elements are of appropriate dimensions. The invention allows cutting to a depth of approximately 50 - 100 mm.

The following is a brief explanation of certain terms and concepts used.

As used herein, a polycrystalline diamond insert (PDC) material contains a plurality of diamond grains, a significant number of which are directly mutually bonded to each other, and in which the diamond content is approximately 80 volume percent of the material. The interstices between the diamond grains may be substantially empty, or they may be at least partially filled with particulate filler, or they may be substantially empty. The particulate filler may contain a sintering aid.

Polycrystalline cubic boron nitride (PCBN) contains grains of cubic boron nitride (cBN) dispersed within a matrix containing metal, semi-metal and/or ceramic material. For example, the PCBN may contain at least 30 volume percent cBN grains dispersed in a matrix material comprising a Ti-containing composition, for example, titanium carbonitride, and/or an Al-containing composition, for example, aluminum nitride, and/ or compounds containing a metal such as Co and/or W. Certain modifications (or "grades") of PCBN may contain at least 80 volume percent or even at least 85 volume percent cBN grains.

Claims (19)

1. The cutting unit of the machine for excavation of rocks, containing: main block, one or more movable support arms extending from the main block, a spindle rotatably attached to said or each movable support arm, a disk cutter fixed relative to the spindle so that the rotation of the spindle causes a corresponding rotation of the disk cutter, moreover, the disk cutter contains a cutter body, a plurality of cutting elements and a corresponding number of tool holders, namely, one for each cutting element, while the cutting elements and tool holders are located around the circumferential surface of the cutter body, each cutting element is placed in the tool holder socket, the socket is oriented so that the cutting element is directed in or towards a given direction of rotation; wherein the cutting element is cylindrical and has a flat cutting surface, said or each cutting element is a polycrystalline diamond insert (PDC), the size in the lateral direction of each cutting element is larger than the size in the lateral direction of the tool holder. 2. A cutting assembly according to claim 1, wherein the tool holders extend radially outward from the cutter body. 3. The cutting assembly according to claim 1 or 2, in which the front angle of the cutting element relative to the tool holder is 10-30 degrees. 4. The cutting unit according to claim 3, in which the front angle is 25 degrees. 5. The cutting unit according to any one of paragraphs. 1-4, in which the tool holder is permanently connected to the cutter body, for example by brazing. 6. The cutting unit according to any one of paragraphs. 1-4, in which the tool holder is detachably connected to the cutter body. 7. The cutting assembly of claim 6, wherein the tool holder is releasably connected to the cutter body by means of a locating pin. 8. The cutting unit according to any one of paragraphs. 1-7, in which each cutting element is permanently fixed in the socket, for example by brazing. 9. The cutting unit according to any one of paragraphs. 1-8, in which the tool holder is generally frustoconical when viewed in the axial direction and has a shorter front side than the back side, with the socket located on the front side. 10. The cutting unit according to any one of paragraphs. 1-9, in which the cutting element protrudes laterally beyond the tool holder by at least 1 mm on each side. 11. The cutting unit according to any one of paragraphs. 1-10, in which each tool holder tapers laterally inward from the cutting element towards the cutter body.

Images